In the drilling of bore holes into or through earth formation, such as in the drilling of oil or gas wells, utilizing a rotary drill bit, it may occur, from time to time, that the bit may be stuck in the earth formation or debris in the bore hole. For example, this may occur either due to the caving in of the bore hole wall, or due to the formation of a key seat in the hard earth formation. When the bit is stuck, under such circumstances, it is difficult, if not impossible, to pull the drill string and bit from the bore hole. In the case of drilling by the usual rotary method, wherein the drill bit is attached to the lower end of a rotary string of drill pipe, it is the practice to rotate the drill pipe by the usual rotary table, as an upward pull is being applied to the drill pipe, to assist in the release of the stuck bit.
In the case of in-hole motor drill assemblies of the electrical or fluid motor types, wherein the rotary drill bit is driven by the in-hole motor interposed between the running string and the bit, there is no positive interlock between the rotor and the drill string, so that it is not possible to cause the bit to rotate by rotation of the running or drill pipe string or fluid conduit above the motor. The reaction torque of such in-hole motors is, generally, taken by a rotary table at the surface of the bore hole, whereby the drill pipe string can either be held stationary or, if desired, rotated to obviate the wedging of the string. If the bit becomes stuck in the bore hole, such in-hole motors will stall and continued rotation of the bit may not be possible, notwithstanding the availability of additional drilling fluid pressure or electromotive force. As a consequence, when an in-hole motor drill has the drill bit stuck in the bore hole, an attempt can be made to pull the running pipe string and the motor drill from the bore hole, without rotating the bit, and various jarring devices have been utilized in the drill pipe string to assist in applying upward jarring forces to the drill pipe string and to the bit, in an effort to dislodge the latter.
In the event that the bit remains stuck, the practice has been to break the drill pipe joint above the motor drill assembly, if possible, in a known manner, whereby the drill pipe string can be retrieved to the drilling rig and, thereafter, to sidetrack the bore hole around the motor and bit which remain in the hole. Such practices result in great losses in time and costs.
Pending application Ser. No. 957,179, filed Nov. 2, 1978, by Trzeciak, relates to an in-hole motor drill apparatus, wherein the rotor of the motor is connected to the drill bit by a rotary drive connection through a clutch between the running string and the bit, including torque transmitting members, which can enable the stator or housing of the motor, in the event that the bit becomes stuck in the hole, to positively transmit torque to the bit, in response to rotation of the drill pipe string.
If the bit is stuck in soft formation, the application of additional weight may interfere with efforts to release the bit because the bit may be forced deeper into the formation in which it is stuck.
Furthermore, the bearing assemblies of in-hole motors have a pick-up or off bottom bearing which transmits upward thrust to the shaft when the housing is elevated to pull the assembly from the bore hole or allow circulation of fluid while the bit is off bottom. Such pick-up bearings normally limit the permissible longitudinal upward movement of the housing relative to the shaft, and, therefore, engagement of a clutch responsive to additional upward movement of the housing requires a predetermined relationship in the structure of the pick-up bearing and the clutch to allow the additional movement required to engage the clutch.
In the application of Crase and Trzeciak, Ser. No. 068,212, filed Aug. 20, 1979, there is disclosed an assembly which permits the necessary longitudinal movement of the housing relative to the shaft for engagement of the clutch, without modification of the pick-up bearing, because a shearable release member is incorporated in the clutch structure. In the companion application of Geczy, Ser. No. 067,882, filed Aug. 20, 1979, there is disclosed a structure wherein the necessary movement of the housing relative to the shaft is resisted by springs, incorporated in the pick-up bearing structure and/or in the clutch structure.